Byrnes
became Secretary of State under Truman, succeeding
Edward Stettinius.
In 1945, Roosevelt invited Byrnes, at that time
still a Senator from South Carolina, to be part
of the Yalta delegation (of which Hiss was a
member) in an effort to include a conservative
viewpoint. Byrnes later publicly opposed some
of the Yalta agreements.

In
1946, Byrnes advised Hiss to talk to the FBI
about rumors that he was a secret communist.
Hiss subsequently was interviewed by the FBI.